1. Field of the Invention
The present invention relates a manufacturing method of a nozzle plate and an ink jet printer head applying the nozzle plate. In particular, the invention relates a manufacturing method of a nozzle plate for an ink jet printer head by etching a silicon substrate and an ink jet printer head manufactured by applying the nozzle plate manufactured by the method.
2. Description of the Prior Art
An ink jet printer head is generally formed by sequential accumulation of a nozzle plate 222 where a nozzle 223 has been formed, a reservoir plate 221 where a reservoir 220 is formed, a channel plate 219 where a flow channel 218 is formed, a restrictor plate 217 where a restrictor 216 is formed, a chamber plate 215 forming a chamber 214, and an actuator composed of three parts of an upper electrode 210, a piezoelectric substance 211 and a lower electrode 212 which is formed on a substrate 213 as in FIG. 1.
By the construction, ink travel paths such as nozzle 223, reservoir 220, flow channel 218, restrictor 216, chamber 214 of mutually different sizes and shapes are formed in the ink jet printer head.
Ink supplied from an ink canister not shown in figure is reserved in the reservoir 220 after which it flows into the chamber 214 through the flow channel 218 whence the reservoir 220 formed between the flow channel 218 and the chamber 214 maintains the ink flow speed into the chamber 214 to a constant state.
The piezoelectric substance 211 is actuated if voltage is applied at the upper electrode 210 and the lower electrode 212 of the actuator formed on the chamber 214; by the actuation of the piezoelectric substance 211, the volume of the chamber 214 momentarily decreases while the ink in chamber 214 is ejected through the nozzle 223 formed in the nozzle plate 222 onto a material on which to be recorded. Printing is carried out by the ejection of ink.
A meniscus, which is exposed to atmosphere at an outlet part of the nozzle plate because of inertial flow of ink for sake of refilling the ejected amount of ink after ink is ejected, takes vibration, and the vibration of the meniscus might be inferred by resonance equation of fluid system.
Because ink cannot be ejected while the meniscus vibrates, it is important to attenuate and stabilize the vibration of the meniscus in a short time in order to decrease the interval until the next ink ejection. The ejection frequency of a printer head can be increased if the vibration of the meniscus can be attenuated in shorter time.
As for a method for attenuating rapidly the vibration of the meniscus, there is generally used method to strengthen the attenuating function by increasing the viscosity of ink or by decreasing the diameter of outlet part of the nozzle plate.
So the outlet part of the nozzle plate is a important factor in an ink jet printer head, affecting the ejecting ability of the ink drop and the stability after ink is ejected.
So far the cross section shape of the outlet part of the nozzle plate was made to have a suitable length of straight part in order to diminish the diameter of the outlet part of the nozzle plate.
The nozzle plate having a suitable length of straight part at the outlet part can rapidly attenuate the vibration of the meniscus because the diameter of the part becomes less than that of other part.
Because the nozzle plate having a suitable length of straight part at the outlet part is to construct a printer head by assembling flow channel, chamber, actuator etc. over itself and the ink flowing through nozzle is made to form laminar flow at straight part when ink is ejected, thus the straight mobility of ink is improved. Therefore dispersion or precision of position, at which point the ink drop lands on material on which to be recorded, is improved so that printed state is improved.
Metal has generally been used as material for nozzle plate wherefore so far method to form the nozzle plate by electroforming and method to form it by micro punching and polishing process have been used in order to manufacture it using a metal.
Photoresist is thinly coated on a substrate and then patterned in electroforming method. If the patterned substrate is immersed in electrolytic solution and is electrified, plating material grows on the substrate; and the plating is stopped if plating material has grown to a nozzle size to use. Whence the plating has been completed, then nozzle plate where nozzle has been formed is completed by removing the substrate and the photoresist that has been formed on the substrate.
A metal sheet for use as a nozzle plate is drawn by micro punching pin to form a nozzle cross section through depth beyond opposite side of the metal sheet, in a method to form the nozzle plate by micro punching and polishing process. Protruded part of the metal sheet after drawing is removed by polishing process; and burr on the metal sheet occurred by polishing process is removed by electrolytic polishing or chemical polishing.
There are cases where a nozzle plate is formed using a single crystal silicon instead of metal in case of continuous type ink jet head or an ink jet head applying thermal expansion of film or bubble jet.
A method for anisotropic etching of silicon in bulk micro machining technique is used in a case of forming the nozzle plate using single crystal silicon as raw material.
As for etching liquid to form a nozzle in silicon substrate by anisotropic etching, anisotropic etching liquid such as potassium hydroxide (KOH) and trimethylamine hydroxide{TMAH} are used by which nozzle is made by forming pyramidal hole in square or circle pattern by anisotropic etching of silicon substrate of (100) crystal direction.
Whence etching can be inhibited for parts other than part to be etched as a nozzle, by way of masking the parts using a silicon oxide film or a silicon nitride film as the shield film.
For this, after masking the parts other than part to be etched, by way of masking the parts using a silicon oxide film or a silicon nitride film, nozzle is made by forming pyramidal hole in silicon substrate of (100) crystal direction using an anisotropic etching liquid.
Whence the shape of nozzle end and the cavity of nozzle are controlled by etching liquid, etching time duration and etching rate of silicon.
Also straight part may be formed by forming a square nozzle on the opposite side using an isotropic etching liquid after anisotropic etching.
But there are problems that the straight forwardness becomes low when ink is ejected in case that a nozzle is formed by being etched only using an anisotropic etching, and that the nozzle formed is not uniform because the degree of etching of each part becomes different as etching is repeated in case that the nozzle plate is formed isotropic etching after anisotropic etching.
Therefore an ink jet printer head applying the nozzle plate has the same problem.
The present invention to solve the above problem aims to provide a method of manufacturing a precise and uniform nozzle plate by anisotropic wet etching applying a high concentration boron layer as the etching interruption layer in forming the nozzle plate by etching the silicon substrate and to provide an ink jet printer head applying the manufactured nozzle plate.
The present invention to achieve the purpose features a method of manufacturing a nozzle plate using a silicon process comprising the steps of: providing a silicon substrate; forming a silicon oxide film on one side of the silicon substrate; patterning the silicon oxide film; performing an anisotropic wet etching on the silicon substrate after shielding the surface of the silicon substrate where silicon oxide film has not been formed; forming a boron layer on surface where silicon oxide film has been formed in the silicon substrate; etching the silicon substrate where the boron layer has been formed; and removing the silicon oxide film and the boron layer formed on the silicon oxide film by etching the silicon oxide film.
Also the present invention features a method of manufacturing a nozzle plate using a silicon process comprising the steps of: providing a silicon substrate; forming a boron layer on one surface of the silicon substrate; masking another surface of the silicon substrate where boron layer is not formed, into a desired pattern; performing an anisotropic wet etching of the patterned silicon substrate; masking the boron layer into a desired pattern; and forming a straight part at the boron layer by way of dry etching of the masked boron layer.
Also the present invention features an ink jet printer head comprising: a substrate; a chamber which is formed under the substrate and which is open only in bottom part; a nozzle plate formed under the substrate and the chamber; a nozzle to record by ejecting ink, formed in the nozzle plate; a boron layer which is formed on the slope of the nozzle and whose end is projected to media side; a lower electrode formed on the substrate; a piezoelectric substance which is formed on the lower electrode and which actuates when voltage is applied; and an upper electrode formed on the piezoelectric substance.
Also the present invention features an ink jet printer head comprising: a substrate; a chamber which is formed under the substrate and which is open only in bottom part; a nozzle plate formed under the substrate and the chamber; a nozzle to record by ejecting ink, formed in the nozzle plate; a boron layer which is formed under the nozzle plate and which forms a straight part at the outlet part of the nozzle; a lower electrode formed on the substrate; a piezoelectric substance which is formed on the lower electrode and which actuates when voltage is applied; and an upper electrode formed on the piezoelectric substance.
Also the present invention features an ink jet printer head comprising: a substrate; a chamber plate formed under the substrate; a chamber formed in the chamber plate; a restrictor plate formed under the chamber and the chamber plate; a restrictor which is formed in the restrictor plate and which makes to maintain the speed of ink flowing into chamber at a constant value; a channel plate formed under the restrictor plate; a flow channel which is formed in the channel plate and which is a travel path of ink; a reservoir plate formed under the channel plate; a reservoir to reserve the ink, formed by the reservoir plate; a nozzle plate formed under the reservoir plate; a nozzle to record by ejecting ink, formed in the nozzle plate; a boron layer which is formed on the slope of the nozzle and whose end is projected to media side; a lower electrode formed on the substrate; a piezoelectric substance which is formed on the lower electrode and which actuates when voltage is applied; and an upper electrode formed on the piezoelectric substance.
Also the present invention features an ink jet printer head comprising: a substrate; a chamber plate formed under the substrate; a chamber formed in the chamber plate; a restrictor plate formed under the chamber plate; a restrictor which is formed in the restrictor plate and which makes to maintain the speed of ink flowing into chamber at a constant value; a channel plate formed under the restrictor plate; a flow channel which is formed in the channel plate and which is a ink travel path; a reservoir plate formed under the channel plate; a reservoir to reserve the ink, formed by the reservoir plate; a nozzle plate formed under the reservoir plate; a nozzle to record by ejecting ink, formed in the nozzle plate; a boron layer which is formed under the nozzle plate and which forms a straight part at the outlet part of the nozzle; a lower electrode formed on the substrate; a piezoelectric substance which is formed on the lower electrode and which actuates when voltage is applied; and an upper electrode formed on the piezoelectric substance.